Asbestos Roof Over-Cladding vs Full Removal for Doncaster Warehouses

For most Doncaster warehouse owners with a tired asbestos cement roof, over-cladding is the better option. It typically costs 40 to 60 per cent less than full removal, keeps the building weathertight and operational throughout, and adds 25 to 40 years of life to the roof. Full removal wins only when the existing structure is too weak to carry a new skin, or when a future redevelopment makes a clean slate the sensible choice.

After 30-plus years working on industrial units across South Yorkshire, we have specified both routes hundreds of times. The right answer always comes down to four things: the condition of the sheets, the strength of the purlins, your budget, and how much downtime you can absorb.

This guide compares the two options honestly. We cover real cost per square metre, the regulations you must satisfy under CAR 2012, and a worked example for a typical 500m² unit so you can see the maths for yourself.

Why Asbestos Cement Roofs Force a Decision

Thousands of industrial units built between 1950 and 1990 across Doncaster, Bentley and the wider South Yorkshire area still have asbestos cement sheeted roofs. The material itself is not dangerous while it stays intact. The problem is age. Cement sheets become brittle, fixings corrode, and hairline cracks let water into the building.

Once a roof starts leaking, patching becomes a losing battle. Every penetration disturbs fragile material, and health and safety rules make even minor repairs expensive. So owners face a fork in the road: strip everything out, or seal the old roof in beneath a new weatherproof layer.

Neither choice is inherently right or wrong. But the cost gap, the disruption gap and the compliance burden differ enormously, and those differences deserve a proper head-to-head comparison rather than a one-line quote.

What Over-Cladding (Encapsulation) Actually Involves

Over-cladding means fitting a new roof directly over the existing asbestos cement sheets. The old roof stays where it is, sealed and undisturbed, while a new outer layer of insulated steel or composite panels takes over the weatherproofing job.

A typical sequence looks like this. First we survey the structure and check purlin spacing and load capacity. Then we install vertical spacer brackets through the old sheets into the purlins. Insulation is laid between, and finally the new profiled or composite sheeting is fixed on top. New guttering, flashings and rooflights complete the envelope, with eaves and ridge ventilation keeping the build-up dry in line with BS 5250.

Because the old sheets are never broken up, the asbestos stays bonded inside the cement. That is what makes encapsulation cheaper and safer for most buildings. You can read more about our approach on our commercial cladding and industrial roofing specialists in Doncaster.

There is a bonus too. The added insulation layer usually improves the thermal performance of the building noticeably, which matters if you heat the unit through a Yorkshire winter.

What Full Removal Involves

Removal means stripping every asbestos cement sheet, fixing and washer from the roof and disposing of it as licensed hazardous waste. The building is open to the elements during the strip, so the work has to happen in reasonable weather, often under temporary cover.

Because the sheets must be broken out, the work sits under the Control of Asbestos Regulations 2012 (CAR 2012). Depending on the scale and condition of the material, you may need a licensed contractor, a 14-day notification to the enforcing authority, and a fully enclosed working zone with decontamination units. Air monitoring and waste transfer documentation add further cost and admin.

Once stripped, you still need a new roof. So removal carries two price tags: the strip and disposal, then the replacement sheeting. That double cost is why removal quotes often come as a shock.

Head-to-Head: Over-Cladding vs Removal

Here is the comparison we walk through with clients on site. Figures are typical UK ranges for industrial asbestos cement roofs and vary with access, height and roof profile.

Cost per Square Metre: What Drives the Price

Roof size is the biggest factor on both routes. Larger roofs cost less per square metre because scaffold, mobilisation and access equipment are spread across more area. As a guide, a 2,000m² roof works out noticeably cheaper per m² than a 400m² one.

Access comes next. A unit on a tight industrial estate off Wheatley Hall Road with no room for a cherry picker will need full scaffolding, and that can add thousands. Height, roof pitch and the number of rooflights and vents all push the price up too. If scaffolding or a skip must sit on the public highway, a City of Doncaster Council licence or skip permit adds days to the programme.

On the removal side, disposal is the wild card. Licensed hazardous waste transfer is charged by the tonne or by the skip, and friable or badly degraded sheets cost more to handle. Wrapped, intact sheets are cheaper to tip than broken material.

On the over-cladding side, insulation thickness is the main variable. Thicker composite or built-up systems cost more up front but cut heating bills for decades. Our commercial roofing service page covers the system options in more detail.

The Regulations: CAR 2012 and Your Duties Explained

Under the Control of Asbestos Regulations 2012, the dutyholder of a non-domestic building must manage asbestos risk. That means knowing what asbestos is present, its condition, and keeping a written asbestos register and management plan available. You can read the official guidance on the HSE asbestos pages.

The regulations bite hardest on removal. Notifiable work requires 14 days advance notice to the enforcing authority. If the work is licensable, only an HSE-licensed contractor may do it. Even non-licensed notifiable work needs trained operatives, proper controls and record keeping.

Over-cladding sits outside most of that because the material is not being removed or substantially disturbed. Drilling through the sheets to fix spacer brackets is controlled work that requires trained operatives, but it avoids the licensing, notification and disposal regime attached to a full strip. That is a genuine, auditable compliance saving, not a loophole.

Worked Example: A Typical 500m² Doncaster Unit

Take a common case from our own patch: a 500m² steel-framed unit with a 10-degree pitched asbestos cement roof, sound purlins, road access for a cherry picker, and a business that cannot stop trading.

• Over-cladding route: new coated steel sheeting over insulated spacer system, new GRP rooflights, new gutter linings. Typically £30,000 to £42,000. Work takes roughly 1 to 2 weeks, the unit stays open, and the roof gains 30-plus years of life.
• Removal route: licensed strip and disposal of around 12 to 15 tonnes of sheeting, plus a new insulated roof. Typically £55,000 to £80,000 all in. Work takes 3 to 4 weeks with periods where the building is exposed.

On these numbers, over-cladding saves £25,000 to £38,000 and around two weeks of trading. Removal buys a clean register and no structural question marks. For an owner-occupier with a sound frame, the over-cladding case is usually compelling. For a site slated for redevelopment, removal often makes more sense.

Choosing a Contractor for Either Route

Whichever option you choose, the contractor matters as much as the system. Ask for evidence rather than assurances. A genuine commercial roofing firm will show you public liability certificates, operative cards and recent comparable jobs without hesitation.

Check five things specifically. Public liability cover of at least £5 million, held in writing. IPAF and CSCS trained operatives for access and height work. Experience with your roof type, asbestos cement needs different handling to steel. A written guarantee, with 20 years being the mark of a quality system. And a detailed method statement before work starts, covering how the site stays safe while your staff are still inside. NFRC membership and CHAS accreditation are two more quick credibility checks before you sign.

Be wary of quotes that arrive without a survey. Prices given over the phone for asbestos work are guesswork, and the variations that matter, purlin condition, sheet fragility, waste volumes, cannot be seen from the ground. A proper survey takes an hour or two and removes the guesswork from a five-figure decision.

When Each Option Wins

Choose over-cladding when

• The asbestos cement sheets are intact and the leaks are age-related, not structural.
• Purlins and rafters are sound and can carry the extra load.
• The business needs to keep trading through the works.
• You want better insulation and lower heating costs in one project.
• Budget matters more than a completely clear asbestos register.

Choose full removal when

• The roof structure is corroded, overloaded or failing.
• The sheets are badly degraded and fragile beyond safe encapsulation.
• You plan to redevelop, extend or sell with a clean asbestos position.
• Your insurer or lender requires removal.
• The purlins cannot take the additional weight of an over-roof.

Frequently Overlooked Details

A few points come up on almost every job once the headline decision is made. They are worth knowing before you commission either route, because they affect the finished result as much as the sheeting itself.

• Ridge and eaves detailing is where over-cladding jobs succeed or fail. New flashings and gutter linings should be included in the quote, not priced as extras later.
• Rooflights should be renewed at the same time. Old GRP rooflights remain the most fragile surfaces on the roof.
• Drainage capacity changes when you add insulation and new gutters. A heavy South Yorkshire downpour soon exposes an undersized gutter.
• Asbestos documentation stays with the building. After over-cladding, your register should record the encapsulation so future owners and contractors know what lies beneath.
• Winter scheduling matters for removal in particular, since an open building and short daylight hours stretch the programme.

None of these are expensive in themselves. They simply need to be in the plan from day one rather than discovered halfway through.

A Practical Decision Checklist

Before you sign anything, work through this list with your contractor. We run through the same points on every survey.

1. Get an asbestos survey so you know exactly what is on the roof and its condition.
2. Ask for a structural check on purlin spacing, section size and corrosion.
3. Request itemised quotes for both routes, including access, disposal and VAT position.
4. Confirm insurance: public liability of at least £5 million and, for removal, the relevant asbestos licence status.
5. Check operative training, IPAF and CSCS cards as a minimum for height work.
6. Ask what guarantee comes with the new roof. Good systems carry 20 years or more.
7. Clarify who handles notification paperwork if removal goes ahead.
8. Agree weather contingency and how the building stays weathertight at every stage.

Our View After 30 Years

Roughly four out of five industrial asbestos roofs we survey in the Doncaster area are better suited to over-cladding. The structure is sound, the sheets are past their best but stable, and the owner wants the problem solved without closing down. Encapsulation delivers exactly that, at a lower price, with far less red tape.

Removal remains the right call for the remainder, and pretending otherwise helps nobody. What matters is that the decision follows a proper survey rather than a guess. If you would like us to look at your unit, we work across Doncaster, Bentley, and all of South Yorkshire, with £5 million public liability cover and guarantees of up to 20 years. Our over-cladding and encapsulation service page explains the next steps.

Common Mistakes to Avoid

Over three decades we have watched the same handful of errors derail otherwise sound projects. Watch for these five.

• Encapsulating with untrained crews. Drilling through asbestos cement to fix spacer brackets is controlled work under CAR 2012. Operatives must be trained and the work properly planned and recorded.
• Skipping the structural check. An over-roof adds load to the purlins. Spacing, section sizes and corrosion must be verified before anyone orders materials.
• Sealing moisture into the build-up. An insulated over-roof without eaves and ridge ventilation traps damp air under the new sheets. BS 5250 sets out the ventilation design.
• Keeping the old rooflights. Aged GRP rooflights stay fragile after over-cladding and remain a fall risk for anyone maintaining the roof. Renew them in the same contract.
• Not updating the asbestos register. The encapsulation must be recorded so future owners and contractors know the sheets remain beneath the new roof.